The present invention relates to the art of electronic component testing. It finds particular application in conjunction with temperature testing of electronic quartz resonators which have a temperature dependent frequency and will be described in the following specification with particular reference thereto. It is to be appreciated, however, that the invention will also find application in conjunction with the testing of other electronic components, both for temperature dependent and other characteristics.
Heretofore, the frequency response of the resonators was measured at a plurality of temperatures to determine frequency response characteristics. Typically, the frequency response was measured three or more times in a temperature range between -50.degree. C. and +150.degree. C. Of course, because the measured response is temperature dependent, accurate measurement of the response requires accurate control of the temperatures to which the components are heated or cooled for testing.
In order to test large numbers of components efficiently, various batch and in-line systems have been developed. In batch systems, the batch of components are all heated or cooled to the same temperature concurrently. The components in the temperature chamber are either stationarily positioned and switched into electrical communication with the test equipment or moved through the temperature chamber to a designated test location. In one prior art batch system with mobile component positioning illustrated in FIG. 1, a multiplicity of components were mounted by hand in sockets facing an inner surface of a cylindrical ring 12 of about 30 centimeters in diameter. The sockets were connected with a series of contact pins 14 which extended radially outward from an outer surface of the cylindrical ring. Once the components were manually loaded into the cylindrical ring, the cylindrical ring was mounted on a motor shaft 16 in a temperature chamber To cool the components, a compressed gas or other coolant from a coolant source 20 was released and controlled by a control valve 22 and pumped into the chamber through a central outlet or port 24 by a blower 26. Once the components were cooled to the selected temperature, the motor shaft 16 was rotated or indexed to bring each of the contact pins 14 into electrical connection with electrical connectors 28. The connectors 28 connected a measurement network 30 and a test instrument 32 with the contact pins 14. After all of the components were tested, the blower blew air across a heater element 34 to warm the components and the test chamber to the next preselected test temperature. A temperature sensor 36 measured the temperature in the test chamber during both cooling and heating cycles and controlled the heater element 32 and the control valve 22 for the coolant source 20 to maintain a constant selected temperature. The cylindrical ring 12 was again rotated and each of the components tested. This same process was repeated at each of the preselected temperatures. After each of the components was tested at each of the temperatures, the components were manually removed and sorted in accordance with the test results.
One of the disadvantages of this system is that the hand insertion, extraction, and sorting was time consuming and expensive. Another disadvantage resided in the wear of the contact pins 14. Typically, the contact pins wore out and required repair or replacement in about a year. Another disadvantage was that part of the hot and cold air could circulate directly from the central port 24, across the temperature sensor 36, and out a return port 38 without reaching the components, causing a reduced efficiency and reliability.
A further disadvantage is that the cylindrical test carriage 12 was expensive and time-consuming to build. A pair of machined profile rings defined the wall of the cylinder to which PC boards were bent and riveted. The boards had an etched pattern for component sockets.
In addition to the temperature testing, the resonators were commonly tested at room temperature for various operating parameters and characteristics. The resonators were moved from the cylindrical carriage used in the temperature testing assembly into a different carriage. One disadvantage, of course, is the time and expense involved in moving the components among test fixtures.
Due to the sensitive nature of the measurements, changes in contact resistance could cause significant errors in the measured parameters and characteristics. As the contacts on the test fixtures wore, it became more difficult to make good, reliable, electrical communication therewith for testing. The lack of assured consistency in the contact resistance was another significant drawback to the prior art systems.
The inconsistent electrical contact resistance is due to serration of the contact pins caused by the cutting action of the contact springs. The resistances may vary from tens of milliohms to several ohms. Depending on wear of the pins, the resistance sometimes increases to infinity, i.e. there is no contact at all. These resistance variations are especially unacceptable for measuring crystal parameters other than the crystal frequency. These parameters are usually measured at room temperature after extracting the crystals from the temperature test ring and inserting them into a separate test system. If the parameters could be measured accurately while still in the ring, they could be measured either in the temperature chamber or, after transfer of the ring, in a separate test system. Either approach would save time and equipment costs. The present invention provides a new and improved system which overcomes the above-referenced problems and others.